Tone stabilizing



July l2, 1932.

R. H. R'ANGER TONE STABILIZING Filed Feb. 26, 1929 nva'vwoz R. H. RANGER Patented July 12, 1932 FES UNITE PATENT orifice ,arenas noWLANn Reivsunor NEWARLWNEW Jnnsa'YQAss'IeNon 'ro nemo ooR ronArIoN or AMERICA, A ooRroRATroN or DELAWARE Tous. sTABiLIzING Application led February 26, 1929.- Serial No. 342,841;

' be accomplished best and mosteffectively at the transmitting end of the signaling sys tem, but it is also possible to compensate for changes in the transmitting frequency at the receiving end of the system. The arrangement, as herein disclosed, is suited and adapted to compensate for changes in the transmitting frequency such as can not clearly be avoided at the transmitter and are occurring irrespective of how much care is tal/:en to maintain absolutely constant frequency at the transmitting end of a system.

Briefly the invention consists in arranging a combination for keeping the frequency or tone at the receiver constant for shifts in incoming Jfrequencies and provides a vplurality of tuned circuits one of which is tuned above and the other of which is tuned below incoming signal frequency. Each of these tuned circuits actuates a. differential relay which, working in combination with a motor, is arranged to shift or change the capacity, the inductance, or change both the capacity and inductancevalue in the circuit of a local oscillator at the receiver or to vary the potential upon the platemember of the local oscillator, so that the resulting frequencies or tones at the receiver will always remain at a constant value, within whateverl predetermined limits may be desired, by using suitable settings of the tuned circuits.

The invention, therefore, has as its primary .object that'of maintaining substantially constant frequencies at a receiving point, or even maintaining constant frequency directly atv the point from` which the energy received is transmitted.

:Other objects are to `provide an arrangement forense -in combination with a receivtbe understood that various modifications may ing system wherein the arrangement of circuits isfrelatively simple and the ,means for maintaining constant frequencies at the re,- ceiver is relatively simple. f

Other objects ofmy invention' are to proviole .circuits and apparatus .for maintaining constant frequencies at a receiving point Awhich utilize only well known ,vacuum tubes and differential relays in combination with the particularlytype of circuits and a suitable'driving means, for example, a motor, for controlling the frequency of a localoscil- .cof

lator circuit, Afonexainple, by lany of :the n methods above set forth.

Stillfother objects of my invention provide, in a manner to. be hereinafter de.- lscribed, a system for maintaining constant tone frequencies at a receiving point which is relatively simple in-its construction and arrangement, eflicient lin its use, compact, .conveniently installed,ifoolproof, and `conveniently operated.

Other objects will at once become ,apparent from a reading of thefollowing 'specifica-- .tion and claims Vwhen read in connection with theaccompanyin-g drawing wherein I,

.have illustrated l.by the single figure there.-

`of one form ofcircuit arrangement which my mventlon may assume?, although it 1s to be made therein and that lv may substitutefor any of the elements shown other suchv elements as have become known in the -art towhich the invention relatesfas losingY full equivalents of those illustrated.l o

Now referring more particularly to the drawing, heterodyne signals are received from a receiver 119 associated with any desired type of antenna` 1217,' or even over a wireline from a receiver, and :are impressed upon the terminals A andB o-f the frequency Y control-system from which they are directed through the primary winding l of a transformer ,member 3. The output energy in thesecondary member ofthetransformer ,3, to which signals from `the receiver are transferred, isthen impressed across the grid and cathode members v9 andy 13' respectively ofthe vacuum ltube amplifier 7,1and thel outputenergy from this tube appearingin the are to z lplate circuit including a plate member 11,

the source of plate potential B+ and the cathode member 13, as well as other elements to be hereinafter defined as being located in the plate circuit, is impressed upon the primary windings 23 and 27 of the transformers 25 and 29 respectively.

Connected in shunt with each of thev prr maries 23 and 27 of the transformers 25 and '29 respectively are transformers 24 and 26 having their primary windings 2O and 22 respectively shunting the primaries 23 and 27. The secondary members and 39 vof the transformers 24 and 26 respectively, together with thevariable capacity elements 37 Vand 41v connected to the ends thereof, form tuned trap vcircuits 31 and 33respectively. The secondary members of the transformers 24 and 26 preferably have a relatively large number of turns as compared with .the number of'turns inthe primaryl windings of these transformers. If, for example," the'V trap circuit 31 is so tuned bymeans of the variablecapacity element37 as to be resonant to a frequency slightlyl above the in- '.coming or received frequency this trap or Arejector circuit 31 will form practically an infinite impedance with regard to this particular frequency and if, for example, the tuned trap or rejector circuit 33 is tuned by means ofthe variablecapacity element 41 f topa frequencyV slightly below the incoming or Y received signal frequency', this trap circuit will form practically an infinite impedance kasregards the particular frequency to which it is tuned. The tuned trapv circuit or frequency trap per se has been disclosed-by my United States Patent No. 1,7 57,333, granted to me-'on May 6,1930. v

This tuning of the separate trap or rejectorcircuits may be accomplished in suchra manner that the energy of the desired frequency which will be passed through the tunedftrap circuitwill stilly be sufficiently far up on the issuing curve to produce effective results.

The transformers 25 and 29 respectively Aare each provided with secondary windings 43 and 45v which connect with two individual branches of the frequency controlv system,

I Ieabch' of which branches may be made selective kfora. specific audio tone,`which is governed v in accordancewith the tuning of the separate trap circuits Y3l and 33. The energy impressed upon the secondary member 33 V`ofthe transformer 25 is impressed inthe usual manner across the grid cathode circuit 0f a vacuum tube amplifier 47 and the energy "impressed in the secondary winding 45 of the 'transformer 29 isV applied across the grid cathode circuit of the vacuumtube ampli- ,fier 49. The-outputs of the vacuum. tube amplifiers 47 and 49'are respectively im- -pressed Vupon the primary windings 51 .and V53 of the transformers 55 and 57 where the energy is transferred to and impressed upon the secondaries 59 and 61 from which it is applied to the rectifiers 63 and 65 respectively.

VThe rectiiiers 63 and 65 may, if desired, bel

ordinary three-electrode. vacuum tubes or may be the simple well known two-element l rectifiers. As shown, I have chosen to illustrate an arrangement wherein it is possible to usevthe ordinary three elementtube as a rectifier suitable to this system, andv thisis provided by connecting the gridV and plate members' 67 and'69 of the tube 63 together, andk also with respect to the tube 65, by conv'necting the grid and plate elements 71 and 77 and y79and throughconductor 77 connects with ,the cathode member ofthe rectie fier tube 65 and throughy conductor 79 and transformer secondary 61Jconnects with the grid and plate elements 71 and 73 -fying tube 65.

ofthe rectif-` Normally, with the received signal exactly Y between vthe Atwo' frequencies, forV whichV the two branches including, respectively, the amplifier 47, and rectifier 63, and theamplifier 49,A and rectier 65, each of the relays 81 and 83, will be actuated on receipt of a Y signal. If, however, the tone of the signal is changedeitheraby the frequency of thetransmitter changing slightly or due to the fact that the local oscillator in thesynchronous detector' or heterodyne detector inthe receiving station changes slightly, the tone will shift up or down. Y If the tone shifts up in frequency to the to-ne of the higher tone frequency system, which has been illustrated as including the amplifier 47 and the rectifier 63, this branch onlyy will actuate its relay, namely, relay 81. A shift down in frequency would accomplish the opposite result, of course, namely, that therelay 83 would be actuated kby the output energy of the rectifier 65 receiving energy from the ampli- Vfier 49 .and m thlscase the higher tuned branch would not actuate the relay 81.

- Thisdifferentiation in the signal pitch, Vir-V ici) respective of the frequency thereof, may now Y be utilized for the purposeof actuating a motor.

A simple reversing connection is 'u madeefromthe two relays 81 and 83 to the armatureof a motor 109, the'iield l111 of which is 'constantly energized vby'a D.-C,

ysource of power, for example, a volt line 1 connected at the terminals 107 and 101,Y ref spectively, where, for the purposes of illustration, it is assumed that the positive ter-` minal is 101 and the negative terminal is A107 The tongues or armatures 85 and V87 of the relays 81 and 83 respectively are connectedto two sides of the armature of the motor. The make contacts 91 and 95 of the two relays are connected together to one side` of the power source through conductors 97 and-99, for example, and in the case herein assumed, these contacts are connected with the plus side of the power source. The space'contacts 89 and 93 of these two relays are then likewise connected to the minus source of power, for example, through the conductors 105-and'103 respectively. `Under these conditions, if the tongues or armatures of both relays 81 and 83 are in the same position, that is, resting upon the space or make contacts, no current flows into the armature of the motor and the motor stands still. rlhis is the condition for a normal signal of a pitch just mid-way between the two tuned branches of the system. W' hen the tongue or armature of onel relay swings to the making contact, while the other remains on the"spacing Contact, the current will flow through the motor in one direction. If the reverse conditions is true, namely, that the other tongue or armature of the other relay` moves while the relay in the first named branch stands still, current will be sent into the armature ofthe motor in a reversedv direction and the motor will thus move in exactly the opposite direction `to that first illust-rated.

The motor 109 is arranged to be made effective for the purpose of controlling the frequency of the received signal by being connected through the connection 113, which may be a worm drive or any other suitable gear reduction system, to a capacity element 115, which is connected in parallel with or forms the condenser of the synchronous detector oscillator, which may be of the Hartley or Colpitts type oscillator. This capacity element is so connected that, for a single tone ch ange in one direction, the motor will change the capacity value in such a manner as to bring Vthe tone frequency down or, for a change in the other direction, the motor will move in such a direction as to bring the tone frequency up. Itis thus seen that the whole arrangement consists of an equalizing or stabilizing device for the tone so that it keeps the tone frequency used in the output circuit 117 of the receiver and amplifier 119 constant within narrow limits.

As there is practically no inertia in the device hunting does not take place.

The arrangement is so connected andy adapted that it is not necessary for one relay to actually stop making contact in order for the motor device to start correcting. lf the signal strength is the least bit different in one relay than it in in theV other, the tongue or armature of that relay will move slightly faster yor slower than that of the other, and .will move in exactly the proper `manner to give small pulses of current in the armature of the motor which will move the capacity element in such a manner as to bring tone frequency back to the normal position midway between the two stabilizing frequencies.

For the purpose of maintaing proper grid bias on the grids of the ampliliersl', 47, and 49 each of these grids is connected through a conductor 19 to a terminal 17 to which is connected a source Q of biasing potential. The cathode members of all the vacuum tubes inthe system may, if desired, be connected in parallel to a common source of energy at the terminals 119 and ,121, and for the purpose of controlling the potential on the various cathodes it is in some cases desirable to have a separate rheostat for each vacuum tube al though this is not essentialto operation. However, as illustrated, a separate rheostat 117 is provided for @ich of the individualV vacuum tubes. Y i K l 1 The invention has been particularly described as being applicable to receivers, but it is ,to be understood that it is not limited thereto and it may be arranged so that a constant frequency is maintained at the point where it is produced, suchV asV at a transmitter, forexample. 1 y

Certain modifications in the above system will atonce suggest themselves to those skilled in the art'A to which the invention relates and I Abelieve myself to'be entitled to make any and all of thesev modifications and changes in'so far as they fall fairly within the spirit and scope of the invention, as definedV by the following claims, wherein :-V

1. A system for maintaining` constant frequency from received signaling impulses whichA includes means for receivingsignals andV producing beat frequencies therefrom, a circuit tuned to a frequency above that of the normal beat frequency resulting from said received signals coupled Ito said receiving means, a circuit tuned to a frequency below that of the normal beat freqeuncy resulting from said received'signals also coupied to said receiving means, andmeans responsiveto the output energy of each ofv said circuits for controlling and maintaining constantV beat frequency from the received signals in laccordance with the differential output energy of each of said circuits.

2. A constant frequency receiving system including signal receiving means for receiv-A ing signals which vary slightly from a deanormal signaling frequency coupled 'withl eo l sired signaling frequency, `a local oscillator said receiving means, a circuit responsive to .beat `frequencies less than those producedV from a normal signaling frequency also coupled-with said receiving means, means dierentially responsive to the output of each'of said circuits'for varying the frequency of the said local oscillator in a direction such that c a constant resulting beat frequency Vis continuallyfmaintained in the receiver from the received signaling impulses, and means for maintaining said changed oscillator frequency permanent forl time periodseq'ualing the time duration betweenV varying received frequencies. Y

j 3. A system for maintaining constant frequencies in a receiverl suitablefor receiving and below the secondary frequency coupled' to the output of the said receiving means, and

means differentially responsive to the output energy from each of said circuits for controlling Vthe frequency of said local oscillator and varying the same'ina direction to maintain permanently a constant yresulting frequency in the yreceiver at all periods for -all received signal frequencies.

'4. Alsystem for maintaining aconstant frequency. from received signals irrespective of variations in the frequency thereof which includes meansrfor receiving signals, a localk oscillator associated with said receiving means for producing beat notes of a predetermined frequency when said local oscillator. frequency'is heterodyned with said received signaling frequency, a circuit tuned toV a frequency above the desired resulting frequency, at circuit tuned to a frequency belowV the desired resulting frequency, means for-coupling each of said circuits with said signal receiving means, and means differentially responsive to the output of each of said tuned circuits for varying the frequency'of the said local oscillator in a direction to con'- tinually maintain constant beat frequencies between the received and locally generated frequencies in the said receiving means.

5. A system for maintaining constant frequencies from received signals irrespective of periodic variation inthe frequency thereof which includes means for receiving signals, a

Vlocaloscillator associated with said receiving I means forproducing beat notes of a predetermined frequency when sai-dV local oscillator frequency is heterodyned *with*r said received signaling frequency, a circuit responsive only to frequenciesfabove the' beat frequency, a circuit responsive only to Vfrequenciesy below the beatfrequency, means for cousion frequency continually varies to aslight Y degree which includes signal receiving means,

a local oscillator associated with said receiving means,'means`f or producingtone frequencies when the frequency of said local oscillator is vheterodyned with said received signaling frequency, circuits kresponsive to energy of a frequency v'above and below that of the resulting tone frequency coupled to Vthe output of'said signal receiving means, 'means for varying the frequency of the said local oscillator, and a differentially operable motor responsive to the output of each of said last named circuits for' operating said frequency `varying means for'said local oscillator to permanently change the yfrequency thereof in direction to maintain constant tone frequencies at each change in the frequency of the receivedfsignals.

' 7. The method'of maintaining constant freasl quenciesin signal receiving systems irrespective of periodic variations inthe frequency of the received signals-which includes receiving signals, generating a local frequency, heterodyning the 'received signals with vthe locally generated frequency,A producing by the said heterodyning beat frequencies of a value` dependent vupon the frequency of the received ico signals, producingjindependent responses in the system'for beat'frequencies above and below thev desired beat'frequency,V periodically raising and lowering the frequency of the locally "generated heterodyne frequency in accordance with a raising and lowering of the beat frequency from that 'desired as pro- 'l duced by the received signals for continually deriving the said predetermined frequency value fromsaid'signal reception, and permanently maintaining the last locallyY generated frequency constant between changes in theY frequency of the received signa-ls.A

' 4 Y RICHARDHOWLAND RANGER, 

